[stylus mode] Fix a crash in indentation code

FIX: Fix a bug where the Stylus mode would crash when queried for indentation.

Closes codemirror/dev#1424

mode/stylus.js

@@ -694,7 +694,7 @@ export const stylus = {
         ch = textAfter && textAfter.charAt(0),
         indent = cx.indent,
         lineFirstWord = firstWordOfLine(textAfter),
-        lineIndent = iCx.lineIndent(iCx.pos),
+        lineIndent = cx.line.indent,
         prevLineFirstWord = state.context.prev ? state.context.prev.line.firstWord : "",
         prevLineIndent = state.context.prev ? state.context.prev.line.indent : lineIndent;